The morphology of dorsal apodemes and endosternites was examined in nine female spider species belonging to eight genera and five families of the infraorder Mygalomorphae in Japan. Dorsal apodemes and endosternites are endoskeletal structures in the cephalothorax that serve as attachment sites for the muscles of chelicerae, pedipalps, legs, and pedicel. Dorsal apodemes are formed by an invagination of the ectoderm, which is externally visible as the fovea, and endosternites are endodermal in origin and possess tendons in some groups, such as Mesothelae and Mygalomorphae. These tendons connect to the sternum, with their attachment sites externally recognizable as sigilla. The morphology of dorsal apodemes was classified into the following four types based on the frontal sectional shape: (1) horizontally plate-shaped, (2) longitudinally teardrop-shaped, (3) longitudinally T-shaped, and (4) longitudinally Y-shaped. The morphology of endosternites was classified into the following two types based on the number of tendons: (1) endosternites with four pairs of tendons and (2) endosternites with two pairs of tendons. This study revealed that differences in the morphology of dorsal apodemes and endosternites correspond to differences in the characteristics of the attached muscles. Moreover, the morphology of the endosternite and its associated muscle attachment patterns exhibited consistency within families and genera that included multiple observed species. Therefore, these structures may serve as fundamental taxonomic traits for establishing higher taxonomic classifications such as families and genera.

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Four new species of Harmonicon F. O. Pickard-Cambridge 1896 are described from the Cerrado biome of Brazil. Three new species are from Tocantins state, in the North region of Brazil: H. arraias n. sp. (♂), H. palmas n. sp. (♂♀), H. tocantins n. sp. (♂), and one new species is from Mato Grosso state, in the Central-west Brazil: H. guimaraes n. sp. (♂♀). Furthermore, we here describe for the first time the male of H. rufescens F. O. Pickard-Cambridge 1896 and expand the distribution range of this species and that of H. candango Wermelinger-Moreira, Castanheira & Baptista 2024.

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A new species of the genus Gnaphosa is described from Japan under the name G. hamabe n. sp. The new species resembles G. kompirensis Bösenberg & Strand 1906. The males of the two species can be distinguished by the structure of the palp, especially the form of the median apophysis, the condition of the membranous portion of the bulb, and the condition of the setae on the sternum. Although females of the two species are similar in the structure of their genital organs, they differ in the condition of the sternum setae and the ratio of labial width to length.

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Geographic variation of a Japanese harvestman species, Leiobunum hiraiwai (Sato & Suzuki 1939) was studied in Tottori Prefecture and adjacent areas in Honshu, Japan. Two geographical races, the Kyushu- Hiroshima race and the Kinki race, both of which differ from one another by the morphology of the male labrum, palps, and penis, have been recorded in the Hiba Mountains of Hiroshima Prefecture and Mt. Hyonosen at the boundary of Tottori and Hyogo Prefectures, respectively. Newly found populations of the species between the two areas，a mountainous area near Mt. Kenashi, in Shinjo-son, Okayama Prefectue, showed characteristics of the Kinki race in all the external characters. However, their karyotypes (2n=20) differed from that of the Kinki race from Mt. Hyonosen (2n=20). A comparison of the 2n = 18 karyotype from the Hiba Mountains with the 2n = 20 karyotype from the Mt. Kenashi area suggests that a centric fusion or fission is responsible for the difference in chromosome number.

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Geographic variation of a Japanese harvestman species, Leiobunum montanum Suzuki 1953 was studied in Tottori Prefecture and adjacent areas in the Chugoku Mountains in Honshu, Japan. In addition to the Mt. Daisen race, occurrence of two new local races were found: “Ohginosen race” which bears typically elongated abdomen and “Chizu-Wakasa race” characterized by having male palps with prehensile structures. The number of chromosomes varied from 2n =18 to 2n = 22 with several populations which show polymorphic for the number. There were many populations that were polymorphic for 2n=20/21/22 in the Chizu and Wakasa areas, southeastern part of Tottori Pref., though no populations fixed for 2n = 22 were found. Populations from Mt. Daisen to the western rim of the Chizu area is characterized by having 2n =18 karyotype, though a population was found to be polymorphic 2n = 18/20. Leiobunum montanum and L. hiraiwai, both of which are members of the curvipalpe-group of Leiobunum, show an exclusive pattern in their distribution except for a few populations where the two occur sympatrically on the northwestern slope of Mt. Hyonosen. This is the case of sympatry found for the first time for two bisexual species of the curvipalpe-group. Leiobunum montanum has body size similar to L. hiraiwai but populations of the Ohginosen race which is sympatric with L. hiraiwai are clearly larger than it. It is likely that the body size difference serves to the sympatric occurrence of the two species.

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Geographic variation of a Japanese harvestman species, Nelima nigricoxa Sato & Suzuki 1939 was studied in Tottori Prefecture and adjacent areas in Honshu, Japan. Populations from the eastern part of the area bear legs with black rings at the base of the femora, whereas those from the western part of the area lacked the black marks. They intergrade one another making a zone of intergradation with ca. 20 km wide in the area roughly flanked by the Koch River and the Sendai River. The position of the zone corresponds well to that between the two races of Gagrellula ferruginea, indicating possible Müllerian mimicry between the two species. No difference across the intergradation zone was found in the other morphological characters. Diploid number of chromosomes varied from 16 to 20 from east to west in the other area in western Tottori Pref. A population polymorphic for the number was found on the northern slope of Mt. Daisen where populations with 2n = 20 and populations with 2n = 18 abut. This indicates occurrence of a chromosomal hybrid zone in the Mt. Daisen area. No significant difference was found in the morphology of labrum, penis, and seminal receptacle, among populations differing in the chromosome number. This suggests that the chromosome rearrangements occurred in this area in the species have effects in neither morphology nor reproductive isolation. Both body and legs became smaller or shorter with the increase of altitude in any of the following four different areas: 1) Mt. Hyonosen, 2) central Tottori west of the Sendai River, 3) Mt. Daisen, and 4) Hino-Nichinan areas, though the correlation between the altitude and leg length is not so clear in the Mt. Hyonosen area.

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Orientzomus luzonicus (Hansen 1905), previously known only from the type specimens collected in the Philippines, is found to occur on Orchid Island. The new specimens are compared with the type series, the species is redescribed based on the newly collected material and mitochondrial COI sequences are provided.

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Dipoenura aplustra (Araneae: Theridiidae), originally described from Hainan, China, is newly recorded from Japan, based on specimens collected in south-central Honshu and southern Shikoku. This discovery expands the known distribution range of the genus Dipoenura to Japan. The present paper provides photographs and illustrations of the species for both sexes, with additional morphological information on the male palp, a detailed diagnosis, and a distribution map.

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A new species, Anaulaciulus kita sp. nov., is described from Hokkaido, Japan. Of the species of the genus Anaulaciulus with known gonopodal morphology, only A. kita sp. nov. and A. koreanus (including its recognized subspecies) share the following combination of three characters: 1) the distal part of the opisthomerite distinctly, not gently, curved outward, the portion distal to the curvature (outward apical process); 2) the apex of this process slightly expanded rather than simply reduced; and 3) a knob-like process and/or a sharp projection (subapical process) present mesally at the base of the outward apical process. However, A. kita sp. nov. is distinguished from A. koreanus by the presence of a linguiform process directed obliquely upward on the outward apical process, and by lacking a subapical process at the base mesally. Mitochondrial COI gene sequences also suggested that A. kita sp. nov. and A. koreanus are distinct species. Although A. kita sp. nov. was collected from March to November, outbreaks and indoor invasions were observed only from late September to October.

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Gynandromorphy has been documented in a variety of spider taxa, including at least fifteen families, but it remains rare relative to the overall diversity of spiders. In this study, we report a case of gynandromorphy in an ant-eating spider, Mallinella sp. (Araneae: Zodariidae), in which a single individual exhibits sexual characteristics of both sexes, along with deformed male and female genitalia. This is the first report of gynandromorphy in the family Zodariidae.

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